1. Field of the Invention
The present invention relates to an impeller assembly for a processing device, such as a pulper or grinder of material. More particularly, the present invention relates to an improvement in the impeller of an impeller assembly, which prevents material that is being processed from lodging in a clearance space between the impeller and stationary walls of the processing device that surround the impeller.
2. Description of the Prior Art
Processing devices that include impeller assemblies are well known. For example, impeller assemblies are used in pulping machines for pulping paper and garbage. Such a pulping machine, including an impeller assembly, is manufactured, for example, by Somat Corp., Pomeroy, Pa., 19367-0128.
As shown in FIG. 1, a prior art processing device 10 includes a drive unit 12, a bearing unit 14 for housing a shaft and bearing assembly (not shown), and a processing unit 16. The bearing unit 14 transmits driving force from the drive unit 12 to the processing unit 16 so as to operate the processing unit 16. Such arrangements are well known and, therefore, will not be described in detail here.
The processing unit 16 houses an impeller assembly 18, which includes a generally circular impeller 20 having a circumferential side face 22 extending between a top face 24 and a bottom face 26 of the circular impeller 20. A plurality of blades 27 are attached to the top face 24 of the circular impeller 20. The blades 27 co-act in known fashion with stationary blades 29 provided on the inner circumferential walls of the processing unit 16 so as to pulp or grind the material put into the processing unit 16.
The material to be processed by the processing unit 16 is moved by the impeller 20 toward an outlet (not shown) when the impeller assembly 18 is rotated by the drive unit 12 through the bearing unit 14. The circumferential side face 22 of the impeller 20 is separated from stationary walls 28 of the processing unit 16 by a clearance space 30. The clearance space 30 permits the impeller 20 to rotate freely inside the processing unit 16 when the impeller assembly 18 is rotated by the driving force transmitted by the bearing unit 14 from the drive unit 12. A perforated screen 32 surrounds the impeller assembly 18 and serves as a filter to limit the size of material passing from the processing unit 14 toward the outlet.
In the known impeller assemblies, as shown in FIG. 1, the impeller 20 has a smooth circumferential side face 22. It has been found that the impeller assembly in such processing devices tends to jam or bind up on the material being processed, in particular plastic and elastic materials, and, therefore, overloads the drive unit. The processing device has to be cleaned often and the impeller assembly removed to correct the jamming condition.